Transition-edge Sensor Microcalorimeters Research Articles

Performance of a bridge-type TES microcalorimeter, excess noise characteristics and dependence of sensitivity on current

Fully utilizing the benefit of strong electrothermal feedback, we achieved the energy resolution of 6.6 eV (FWHM) at 5.9 keV and a fast response time of 74 μs with our bridge-type Ti/Au transition-edge sensor (TES) microcalorimeter. The energy resolution of this device was limited by a noise that was larger than the intrinsic noise and the readout noise. This noise only appeared when the current through the TES was large (≳10 μA) , and its level, defined as a fluctuation amplitude of the current through the TES, was in proportion to the inverse of the TES resistance. We also found that the TES sensitivity depended on the current through the TES, normalized with the critical current of the TES. When the current exceeded about 1% of the critical current, the TES sensitivity was significantly degraded. The critical current clearly correlated with the TES sensitivity, and hence the signal-to-noise ratio at the optimal operating point, among devices with different TES size and thickness. Thus, the critical current is one of the key parameters to determine the performance of the TES microcalorimeter.

Application of a TES micro-calorimeter as high-energy resolution detector for hard X-rays at a synchrotron beam line

A superconducting transition edge sensor microcalorimeter was tested at the synchrotron radiation beam-line of the ESRF to collect the X-ray fluorescence spectrum of a Renaissance gold lustre on ceramic. The measured energy resolution of the detector in the range 6–9keV was 70eV, i.e. 3 times better than that of the usual solid state detector. The preliminary data collected demonstrate the applicability of these detectors to the energy dispersive X-ray spectroscopy at the synchrotron radiation facilities.

Frequency-domain multiplexing of TES microcalorimeter array with CABBAGE

Properties of Transition-Edge Sensor (TES) microcalorimeters operated with AC bias are studied utilizing the calorimeter Wheatstone bridge circuit called Calorimeter Bridge Biased by an AC Generator (CABBAGE). The CABBAGE eliminates the AC carrier significantly, thus enables us to study the AC responses of the TES with high sensitivity. We tested two kinds of TES devices operating at 110 and 440mK, respectively. With the 110mK device biased with 25kHz, an energy resolution of 28eV is obtained for Mn Kα line. On the other hand, we multiplexed the signals from two 440mK device biased with 50 and 20kHz, respectively, and obtained 167 and 271eV energy resolutions. Even at the balance point of the bridge, AC signal did not disappear and odd-order harmonics were observed. They are considered to arise from the current dependence of the TES resistance, which is characterized by β≡dlogR/dlogI. Numerical solution for the CABBAGE response can reproduce the experimental results well if β=0.24±0.02. Since the harmonics may cause severe problem in the SQUID operation even after attenuated by a band-pass filter, especially at high bias frequency operation such as several hundred kHz, it is important to make β small.

Demonstration of a low-noise near-infrared photon counter with multiphoton discrimination

We have demonstrated a system capable of directly measuring the photon-number state of a single pulse of light using a superconducting transition-edge sensor microcalorimeter. We verify the photon-number distribution of a weak pulsed-laser source at 1550 nm. Such single-photon metrology at telecommunication wavelengths provides the foundation for ensuring the security of photon sources used in implementations of quantum cryptography. Additionally, this system has the lowest noise equivalent power of any single-photon detector and combines high efficiency near-infrared photon counting with the ability to resolve multiphoton absorption events.

Noise analysis of gamma-ray TES microcalorimeters with a demonstrated energy resolution of 52 eV at 60 keV

We present recent results from our /spl gamma/-ray transition-edge sensor (TES) microcalorimeters. We have demonstrated an energy resolution of 52 eV at 60 keV with devices composed of a high-purity Sn absorber and a Mo/Cu multilayer thin-film TES. In this paper, we present a detailed noise analysis of these devices and show that the major noise sources are device originated (thermal fluctuation and Johnson noise). Our performance analysis explicitly includes the noise contribution due to the composite geometry of these devices and electro-thermal feedback (ETF).

Noise properties of serial SQUID array amplifiers for transition edge sensor

We report on the noise properties of serial SQUID arrays (SSAs). We have developed current amplifiers using SSAs for transition edge sensor microcalorimeters with high current resolution and large dynamic range. Some SSAs changing the number of DC-SQUIDs were fabricated. Distortions on the Φ– V curves did not occur for all SSAs. Current resolution better than 10 pA/√ Hz was obtained by SSA amplifiers composed of 200 DC-SQUIDs or more. For SSAs composed of DC-SQUIDs having same device parameters, the current resolution is improved as the number of the DC-SQUIDs is increased. However, it is limited by a certain number, which does not only depend on the voltage noise of RT electronics but also on the noise generated in SSA itself.

The Microcalorimeter for Industrial Applications.

To achieve the dramatic increases in x-ray spectral resolution (<20 eV at 1.5k eV) desired by market segments such as the semiconductor industry, NIST developed a transition-edge sensor (TES) microcalorimeter. To bring this exciting, yet demanding, new technology to the industrial users, certain criteria must be addressed. Aspects of resolution, cooling and hold time, count rates as well as vibrations are considered. Data is presented to the present efforts to handle these issues as well as discussing development plans for the future.

Superconducting transition-edge-microcalorimeter X-ray spectrometer with 2 eV energy resolution at 1.5 keV

We describe the operation and performance of a prototype microcalorimeter “energy-dispersive” (non-dispersive) X-ray spectrometer (μcal EDS) developed at NIST for use in X-ray microanalysis and X-ray astronomy. The low-energy microcalorimeter detector, consisting of an Al–Ag bilayer superconducting transition-edge sensor (TES) in thermal contact with a Bi X-ray absorber, is designed for operation in the energy range from 0–2 keV and is fabricated using a shadow-mask lithographic process. The TES microcalorimeter is cooled by a compact adiabatic demagnetization refrigerator and is mounted on a scanning electron microscope. This device achieves a best energy resolution of 2.0±0.1 eV at 1.5 keV, as determined from the analysis of digitized X-ray spectra of a complex glass containing many elements.

Characteristics of Ti films for transition-edge sensor microcalorimeters

We are developing X-ray microcalorimeters using superconducting transition-edge sensors (TESs), which can be operated at relatively high base temperatures of a 3 He cryostat. For this purpose, we have selected Ti films to be used as TESs. The Ti films were deposited on different substrates by RF-sputtering. It was found that the superconducting properties of the Ti films depended on Ar pressure, film thickness, and substrate surface roughness.